是否可以用开关替换if( .. instanceof ...), elseif(... instanceof ...), ...的块？
例如：
<?php
$class = ..... //some class
if($class instanceof SomeClass) {
//do something
} elseif($class instanceof SomeAnotherClass) {
//do something else
}
对于考虑继承的具有instanceof的多态交换机：
switch(true) {
case $objectToTest instanceof TreeRequest:
echo "tree request";
break;
case $objectToTest instanceof GroundRequest:
echo "ground request";
break;
}
对于类名应该完全匹配的交换机：
$class = get_class($objectToTest);
switch($class) {
case 'TreeRequest':
echo "tree request";
break;
case 'GroundRequest':
echo "ground request";
break;
}
以下更正确：
$class = get_class($objectToTest);
switch($class) {
case TreeRequest::class:
echo "tree request";
break;
case GroundRequest::class:
echo "ground request";
break;
}
通过这种方式可以正确地比较名称空间（您不必键入它们），如果名称空间或类名等发生任何更改，您将收到一个相当不错的IDE错误，通知您的代码已损坏。
使用match表达式，它看起来像这样：
return match(get_class($object)) {
TreeRequest::class => "tree request",
GroundRequest::class => "ground request",
default => "default request"
}
请记住，它错过了继承，只接受当前类。考虑继承的匹配表达式：
return match(true) {
$object instanceof TreeRequest=> "tree request",
$object instanceof GroundRequest => "ground request",
default => "default request"
}